Self-powered sensor device

ABSTRACT

A sensor device includes an image sensing array, a frame buffer, a first read line, a second read line and an energy accumulator. The image sensing array is configured to sense reflected light from a working surface and includes a plurality of sensing pixels and a plurality of self-powered pixels. The sensing pixels respectively output image data according to the sensed reflected light. The self-powered pixels respectively output photocurrent according to the sensed reflected light. The first read line is coupled between the sensing pixels and the frame buffer. The second read line is coupled between the self-powered pixels and the frame buffer. The energy accumulator stores electrical energy of the photocurrent via a charge path between the self-powered pixels and the energy accumulator.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 15/283,842, filed on Oct. 3, 2016, which claims the priority benefitof Taiwan Patent Application Serial Number 105102500, filed on Jan. 27,2016, the full disclosure of which is incorporated herein by reference.

BACKGROUND 1. Field of the Disclosure

This disclosure generally relates to an optical mouse device, moreparticularly, to a self-powered optical mouse device and an operatingmethod thereof.

2. Description of the Related Art

An optical mouse device usually includes a light source and an imagesensor. In power consumption of the optical mouse device, a light sourceconsumes the greatest part of the power consumption. Therefore, how tolower the power consumption of the light source is an important issue.

Conventionally, when the optical mouse device is not operated for aperiod of time, total power consumption can be lowered by lowering theintensity of illumination of the light source or data retrieving speedof the image sensor.

However, as mentioned above, so far optical mouse devices are designedas lowering the power consumption but not designed to feed opticalenergy of the light source back to supplying power of the optical mousedevices in operation.

Accordingly, the present disclosure provides an optical mouse devicewhich can provide a part of the optical energy of the light source aselectrical energy for operating the optical mouse device so as toimprove the utilization efficiency of energy.

SUMMARY

The present disclosure provides an optical mouse device which converts apart of light energy of a system light source included therein toelectrical energy for operating the optical mouse device.

The present disclosure provides a sensor device capable of improving theenergy utilization efficiency. The sensor device is configured to beoperated on a working surface. The sensor device includes an imagesensing array, a frame buffer, a first read line, a second read line andan energy accumulator. The image sensing array is configured to sensereflected light from the working surface and includes a plurality ofsensing pixels and a plurality of self-powered pixels. The plurality ofsensing pixels is configured to respectively output image data accordingto the sensed reflected light. The plurality of self-powered pixels isconfigured to respectively output photocurrent according to the sensedreflected light. The first read line is coupled between the sensingpixels and the frame buffer to output the image data to the framebuffer. The second read line is coupled between the self-powered pixelsand the frame buffer to output the photocurrent to the frame buffer. Theenergy accumulator is configured to store electrical energy of thephotocurrent via a charge path between the self-powered pixels and theenergy accumulator.

The present disclosure further provides a sensor device configured to beoperated on a working surface. The sensor device includes a framebuffer, an energy accumulator and an image sensing array. The imagesensing array is configured to sense reflected light from the workingsurface and includes a plurality of sensing pixels and a plurality ofself-powered pixels. The plurality of sensing pixels is configured torespectively output image data according to the sensed reflected light,each of the sensing pixels having a read switch configured to controlthe outputting of the image data to the frame buffer. The plurality ofself-powered pixels is configured to respectively output photocurrentaccording to the sensed reflected light, each of the self-powered pixelshaving an energy storage switch configured to control the outputting ofthe photocurrent to the energy accumulator to cause the energyaccumulator to store electrical energy of the photocurrent.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, advantages, and novel features of the present disclosurewill become more apparent from the following detailed description whentaken in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram of an optical mouse device according toone embodiment of the present disclosure.

FIGS. 2A-2C are schematic diagrams of the pixel arrangement of an imagesensing array according to some embodiments of the present disclosure,wherein the image sensing array includes self-powered pixels.

FIG. 3 is a flow chart of an operating method of an optical mouse deviceaccording to one embodiment of the present disclosure.

FIG. 4 is an operational schematic diagram of an operating method of afirst mode of an optical mouse device according to one embodiment of thepresent disclosure.

FIG. 5 is an operational schematic diagram of an operating method of asecond mode of an optical mouse device according to one embodiment ofthe present disclosure.

FIG. 6 is a schematic diagram of a pixel circuit according to oneembodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENT

It should be noted that, wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Please refer to FIG. 1, it is a schematic diagram of an optical mousedevice 1 according to one embodiment of the present disclosure. Theoptical mouse device 1 includes a light source 11, an image sensingarray 12, a frame buffer 13, an energy accumulator 14 and a processor15. In some embodiments, the optical mouse device 1 is operated on aworking surface S and configured to detect a movement relative to theworking surface S.

The light source 11 is, for example, an active light source configuredto emit light of identifiable spectrum for illuminating the workingsurface S. In some embodiments, the light source 11 is, for example, alight emitting diode or a laser diode configured to emit red lightand/or infrared light. In some embodiments, the optical mouse device 1further includes an optical element, such as a lens configured to adjustan illumination field of the light source 11.

The image sensing array 12 is, for example, included in an image sensor,and configured to sense light energy of reflected light of the lightsource 11 reflected by the working surface S. The image sensor is, forexample, an active sensor including a substrate layer. The substratelayer is manufactured by the semiconductor process to include aplurality of sensing pixels and a plurality of self-powered pixels(described hereinafter in detail). The sensing pixels are configured torespectively output image data If according to sensed light energy ofthe reflected light, and the self-powered pixels are configured torespectively output photocurrent Ip according to sensed light energy ofthe reflected light.

In the present disclosure, the image data If is configured to beprovided to the processor 15 for calculating a displacement. Forexample, the processor 15 calculates the displacement by comparing theimage data If of two image frames, wherein an image frame is referred tothe image data If outputted by scanning the sensing pixels within onescanning period. The sensing pixels may have conventional pixelstructures having three transistors (3T) or four transistors (4T)without particular limitations. For example, the sensing pixels have thepixel structure of conventional CMOS image sensors.

In the present disclosure, the photocurrent Ip is configured to beprovided to the light source 11 for emitting light. For example, theself-powered pixels are coupled to at least one energy accumulator 14,which is configured to store electrical energy of the photocurrent Ip,wherein the electrical energy is mainly configured to be provided to thelight source 11, but not to limited thereto. In some embodiments, theoptical mouse device 1 includes, for example, a capacitor as the energyaccumulator 14. All of the self-powered pixels are coupled to thecapacitor. In some embodiments, the optical mouse device 1 includes, forexample, a plurality of capacitors as the energy accumulator 14. Theself-powered pixels are divided into a plurality of regions, and theself-powered pixels in each region are coupled to one capacitor, e.g.,each row or column of self-powered pixels is coupled to one capacitor,but not limited thereto. The at least one energy accumulator 14 iscoupled to the light source 11, and configured to provide the storedelectrical energy to the light source 11 for illuminating light.

The processor 15 is, for example, a digital signal processor (DSP), amicrocontroller or an application specific integrated circuit (ASIC).The processor 15 is configured to calculate a displacement according tothe image data If outputted by the sensing pixels, e.g., calculating thedisplacement according to the correlation between two image frames, andidentify an operation mode. When the calculated displacement is largerthan a displacement threshold, a first mode is maintained; whereas, whenthe displacement is smaller than the displacement threshold, a secondmode is entered. In the present disclosure, the first mode is referredto, for example, a mode that the processor detects displacements andoutputs the displacements at a report rate. The second mode is referredto, for example, a mode that the processor 15 detects the optical mousedevice 1 being substantially at a steady state, and the operation of atleast a part of components is slowed down or disabled. It should bementioned that the first mode is referred to a normal mode, and thesecond mode is referred to a sleeping mode herein, but not limitedthereto. The normal mode and the sleeping mode are only intended toillustrate states of different modes.

In the present disclosure, in the first mode the sensing pixels and theself-powered pixels are both in operation; whereas, in the second modethe sensing pixels are deactivated (or turned off) and the self-poweredpixels are continuously in operation (or turned on). It means that theself-powered pixels output the photocurrent Ip in both the first modeand second mode, and the photocurrent Ip generated in different modesmay have different functions. The sensing pixels being deactivated inthe second mode is referred to not outputting the image data If. Forexample, the transistor in the pixel circuit for controlling theoutputting of the image data If is not conducted, and the sensing pixelsoutput the image data If only in the first mode.

The frame buffer 13 is, for example, a volatile memory or a buffer, andconfigured to store the image data If outputted by the sensing pixels orstore intensity data corresponding to the photocurrent Ip outputted bythe self-powered pixels. To be more precisely, in the presentdisclosure, the frame buffer 13 is, in the first mode, coupled to thesensing pixels but not coupled to the self-powered pixels so as to storethe image data If outputted by the sensing pixels. The frame buffer 13is, in the second mode, coupled to the self-powered pixels but notcoupled to the sensing pixels so as to store the intensity datacorresponding to the photocurrent Ip outputted by the self-poweredpixels, wherein the intensity data is also referred to gray values.

In one embodiment, the optical mouse device 1 includes, for example, amultiplexer 17 coupled between the frame buffer 13 and the self-poweredpixels as well as the sensing pixels. When the processor 15 identifiesthat the first mode is entered, the processor 15 controls themultiplexer 17 to electrically connect the frame buffer 13 to thesensing pixels to temporally store the image data If. When the processor15 identifies that the second mode is entered, the processor 15 controlsthe multiplexer 17 to electrically connect the frame buffer 13 to theself-powered pixels to temporally store the intensity data associatedwith the photocurrent Ip. It should be mentioned that using amultiplexer is just one embodiment, and the present disclosure is notlimited thereto. It is possible to use other switches as long as thepurpose of switching can be implemented.

The processor 15 is configured to calculate the displacement accordingto the image data If in the frame buffer 13, and identify whether toleave the second mode according to a value variation of the intensitydata stored in the frame buffer 13. As mentioned above, in the secondmode the self-powered pixels store the intensity data related to thephotocurrent Ip into the frame buffer 13, and the processor 15 comparesa value variation of the intensity data corresponding to photocurrent Ipbetween two image frames, wherein one image frame refers to photocurrentIp outputted by scanning the self-powered pixels within one scanningperiod. In the present disclosure, a frame rate of the self-poweredpixels is lower than that of the sensing pixels. When a value variationof the intensity data exceeds a variation threshold, it means that theoptical mouse device 1 has a movement, and thus the processor 15identifies that the second mode should be left. When the value variationof the intensity data does not exceed the variation threshold, it meansthat the optical mouse device 1 is not moved, and thus the processor 15identifies that the second mode should be maintained. In someembodiments, the processor 15 calculates a correlation between intensitydata related to photocurrent Ip of two image frames. When thecorrelation is lower than a predetermined threshold, it means that amovement occurs; on the contrary, no movement occurs. Furthermore, it ispossible to identify the value variation by using other conventionalways without particular limitations, such as identifying a similaritybetween two image frames.

Please refer to FIGS. 2A to 2C, they are schematic diagrams of the pixelarrangement of an image sensing array 12 according to some embodimentsof the present disclosure. As mentioned above, the image sensing array12 includes a plurality of sensing pixels 121 and a plurality ofself-powered pixels 122. In some embodiments, the self-powered pixels122 are arranged in a part of pixel rows (e.g., FIG. 2B) or pixelcolumns (e.g., FIG. 2A), and the plurality of pixel rows or pixelcolumns of the self-powered pixels 122 are not adjacent to each other.As shown in FIGS. 2A and 2B, one row (or column) of sensing pixels 121is arranged between two rows (or columns) of self-powered pixels 122. Insome embodiments, the sensing pixels 121 and the self-powered pixels 122are arranged as a checkerboard pattern, as shown in FIG. 2C.

As mentioned above, the processor 15 is configured to calculate adisplacement according to image data If outputted by the sensing pixels121. As the sensing pixels 121 are not completely adjacent to eachother, the processor 15 further performs an interpolation on the imagedata If before calculating the displacement and calculates thedisplacement according to the interpolated image data to improve thecalculation accuracy.

For example, when pixels of the image sensing array 12 are arranged asthose shown in FIG. 2C, pixel data of a pixel position (1, 2) isobtainable by interpolating pixel data of pixel positions (1, 1), (2, 2)and (1, 3), and pixel data of a pixel position (1, 4) is obtainable byinterpolating pixel data of pixel positions (1, 3) and (2, 4), and soon. It should be mentioned that a method of the interpolation is notlimited to those given in the present disclosure.

Please refer to FIGS. 2A to 2C again, the optical mouse device 1includes, for example, a read circuit coupled to the image sensing array12 and configured to read pixel data of the sensing pixels 121 andself-powered pixels 122. The read circuit is, for example, a correlateddouble sampling circuit, and coupled with two read lines. One of theread lines is coupled to the sensing pixels 121 and the frame buffer 13,and configured to output image data If. The other one of the read linesis coupled to the self-powered pixels 122 and the frame buffer 13, andconfigured to output photocurrent Ip. Furthermore, the optical mousedevice 1 further includes a charge path which is coupled to theself-powered pixels 122 and the energy accumulator 14, and configured tostore the photocurrent Ip to the energy accumulator 14, wherein thecharge path forms, for example, a bus to transport the photocurrent Ipoutputted by a part or all of the self-powered pixels 122. As mentionedabove, the optical mouse device 1 further includes a switching device(e.g. the multiplexer 17) to switch between different connections in afirst mode and a second mode to couple the frame buffer 13 to theself-powered pixels 122 or to the sensing pixels 121. In addition,analog to digital convertors (ADC) 16 and 16′ are arranged between theread circuit and the frame buffer 13 for converting the pixel data intodigital signals to be stored in the frame buffer 13.

Please refer to FIG. 3, it is a flow chart of an operating method of anoptical mouse device according to one embodiment of the presentdisclosure. The operating method is adaptable to the optical mousedevice 1 as shown in FIG. 1. In a first mode, a light source 11illuminates a working surface S, and an image sensing array 12 includinga plurality of sensing pixels 121 and a plurality of self-powered pixels122 is configured to sense light energy of reflected light from theworking surface S. The sensing pixels 121 are coupled to a frame buffer13 and configured to store the image data If into the frame buffer 13.The processor 15 reads the image data If from the frame buffer 13 tocalculate a displacement. The self-powered pixels 122 are coupled to atleast one energy accumulator 14 and configured to store electricalenergy of the photocurrent Ip to the energy accumulator 14. The energyaccumulator 14 is, for example, coupled to the light source 11 toprovide electrical energy required in the illumination of the lightsource 11.

The operating method of the present disclosure includes the steps of:emitting light by a light source (step S30); calculating a displacementaccording to image data outputted by a plurality of sensing pixels (stepS31); entering a second mode when the displacement is smaller than adisplacement threshold (step S32); deactivating the sensing pixels inthe second mode (step S33); respectively outputting photocurrent by aplurality of self-powered pixels (step S34); and storing electricalenergy of the photocurrent into at least one energy accumulator to beprovided to a light source for light illumination (step S35).

Please refer to FIGS. 3 and 4, FIG. 4 is an operational schematicdiagram of a first mode of an optical mouse device according to oneembodiment of the present disclosure. In the first mode, the sensingpixels 121 sense light energy of the light source 11 to respectivelyoutput image data If to the frame buffer 13. The processor 15 thencalculates a displacement according to the image data If (Steps S30,S31). As mentioned above, as the sensing pixels 121 are not continuouslyarranged, preferably the processor 15 performs an interpolation on theimage data If before calculating the displacement to correctly obtainthe displacement. When the processor 15 identifies that the displacementis larger than a displacement threshold, the optical mouse device 1keeps on operating in the first mode. When the processor 15 identifiesthat the displacement is smaller than the displacement threshold, theoptical mouse device 1 enters a second mode (Step S32), e.g.deactivating (or turning off) the sensing pixels (Step S33) and slowingdown or turning off the operation of a part of components. Afterentering the second mode, the self-powered pixels 122 continuouslyoperate.

In the first mode, the self-powered pixels 122 sense light energy of thelight source 11 and output photocurrent Ip to the at least one energyaccumulator 14 (Steps S30, S34). The electrical energy stored in the atleast one energy accumulator 14 from the photocurrent Ip is configuredto provide operating energy of the optical mouse device 1 (Step S35),e.g., required in the illumination of the light source 11, but notlimited thereto. It is possible to provide the electrical energy toother components of the optical mouse device 1.

Please refer to FIG. 5, it is an operational schematic diagram of asecond mode of an optical mouse device according to one embodiment ofthe present disclosure that is also adaptable to the optical mousedevice 1 in FIG. 1. In the second mode, the self-powered pixels 122sense light energy of reflected light from the working surface S andgenerates photocurrent Ip. Similar to the first mode, the self-poweredpixels 122 are coupled to at least one energy accumulator 14 which isconfigured to store energy of the photocurrent Ip being generated. Theenergy accumulator 14 is, for example, coupled to the light source 11 toprovide the stored electrical energy to the light source 11 for lightillumination. In addition, in the second mode, the self-powered pixels122 are coupled to the frame buffer 13 to store the pixel data into theframe buffer 13 to be provided to the processor 15 for post-processing.To be more precisely, in the second mode, the self-powered pixels 122may be coupled only to the frame buffer 13 or coupled to both the framebuffer 13 and the at least one energy accumulator 14.

In some embodiments, in the second mode the self-powered pixels 122output intensity data corresponding to photocurrent Ip to be stored inthe frame buffer 13. The processor 15 calculates a variation of theintensity value according to the intensity data to confirm whether toleave the second mode or not. For example, when a value variation of theintensity data is smaller than a variation threshold, the optical mousedevice 1 maintains the operation in the second mode. When a valuevariation of the intensity data is larger than a variation threshold,the second mode is ended and the sensing pixels 121 are activated (orturned on) again to enter the first mode.

The value variation is, for example, referred to a value variation ofthe intensity data in two successive image frames compared by theprocessor 15 pixel-by-pixel. When a number of pixels, whose valuevariation exceed a variation threshold, is larger than a predeterminednumber, the second mode is identified to be left or ended.

It another embodiment, the processor 15, for example, calculates anaverage value of the intensity data of every frame, and when a valuevariation of the average value exceeds a variation threshold, the secondmode is identified to be left or ended.

In another embodiment, the processor 15, for example, calculates adisplacement according to the intensity data (as calculating thedisplacement according to image data If). When the calculateddisplacement is larger than a predetermined displacement, the secondmode is identified to be left, wherein when the processor 15 calculatesthe displacement according to the intensity data, the processor 15further performs an interpolation before calculating the displacement.

To save more electrical energy, the illumination intensity of the lightsource 11 in the second mode is selected to be lower than that in thefirst mode.

In the present disclosure, the image frame in the second mode is formedby pixel data outputted by the self-powered pixels 122, and the imageframe in the first mode is formed by pixel data outputted by the sensingpixels 121.

Please refer to FIGS. 4 and 5, a plurality of self-powered pixels 122are coupled to at least one energy accumulator 14 in both the first modeand the second mode, and output electrical energy of photocurrent Ip tobe stored in the energy accumulator 14. The energy accumulator 14 is,for example, coupled to a light source 11 and provides electrical energyrequired in the illumination of the light source 11. In the second mode,the self-powered pixels 122 are further coupled to the frame buffer 13to provide pixel data to the processor 15 for being further calculatedto identify whether to leave the second mode or not.

Please refer to FIG. 6, it is a schematic circuit diagram of a pixelcircuit according to one embodiment of the present disclosure. Asmentioned above, the sensing pixels 121 may have conventional pixelstructures having three transistors (3T) or four transistors (4T)without particular limitations. For example, the sensing pixels 122include a photodiode 61, an energy storage structure 62 (for example,not limited to, a capacitor, a storage node or a floating diffusionnode) and a read switch 631. The photodiode 61 is configured to convertoptical energy to electrical energy. The energy storage structure 62 isconfigured to temporally store the electrical energy converted by thephotodiode 61. The read switch 631 is configured to control theoutputting of the electrical energy (i.e. image data If) stored in theenergy storage structure 62 according to a row selection signal Sr to areadout line 64. The readout line 64 is, for example, coupled to theread circuit (as shown in FIGS. 2A to 2C) to store the outputted imagedata If to the frame buffer 13.

A pixel structure of the self-powered pixels 122 is not particularlylimited. In addition to the photodiode 61, the energy storage structure62 and the read switch 631, the self-powered pixels 122 further includesan energy storage switch 632 configured to output the photocurrent Ipconverted by the photodiode 61 to the energy accumulator 14 according toan energy storage signal Sh, wherein the row selection signal Sr and theenergy storage signal Sh are provided, for example, by a timingcontroller to simultaneously or sequentially conduct the correspondingswitch. Similarly, the photodiode 61 is configured to convert lightenergy to photocurrent Ip. The read switch 631 is configured to controlthe photocurrent Ip to be outputted to a readout line 64. The readoutline 64 is, for example, coupled to the read circuit (as shown in FIGS.2A to 2C) to store the outputted photocurrent Ip to the frame buffer 13.Therefore, the photocurrent Ip converted by the photodiode 61 is able tobe outputted to the energy accumulator 14 and/or the frame buffer 13 indifferent operation modes.

It should be mentioned that although descriptions above are explainedusing a mouse device operated on a table, the present disclosure is notlimited thereto. In some embodiments, an image sensing array 12 of thepresent disclosure is also adaptable to, for example, an optical systemincluding a system light source, such as an optical finger mouse or aproximity sensor so as to reuse a part of electrical energy.

The optical mouse device 1 of the present disclosure further includes atiming controller or a signal generator configured to generate timingsignals to control the read circuit to read pixel data (including theimage data If and photocurrent Ip) and control the on/off of everyswitching device (e.g., 17, 631 and 632).

The optical mouse device 1 further includes, for example, an outputinterface to output, at a report rate, the displacement calculated bythe processor 15 to a host to correspondingly control a cursor movement.In some embodiments, the report rate is adjustable according to softwarecurrently operated by the host.

As mentioned above, the conventional optical mouse device does not havethe electrical energy feedback mechanism, so the energy saving of totalpower consumption has an upper limit. Therefore, the present disclosurefurther provides a self-powered optical mouse device (as shown in FIGS.1, 2A to 2C) and an operation method thereof that is able to store apart of light energy of a light source and feedback the stored energy tothe light source to significantly improve the energy utilizationefficiency of the optical mouse device.

Although the disclosure has been explained in relation to its preferredembodiment, it is not used to limit the disclosure. It is to beunderstood that many other possible modifications and variations can bemade by those skilled in the art without departing from the spirit andscope of the disclosure as hereinafter claimed.

What is claimed is:
 1. A sensor device configured to be operated on aworking surface, the sensor device comprising: an image sensing arrayconfigured to sense reflected light from the working surface, the imagesensing array comprising: a plurality of sensing pixels configured torespectively output image data according to the sensed reflected light;and a plurality of self-powered pixels configured to respectively outputphotocurrent according to the sensed reflected light; a frame buffer; afirst read line coupled between the sensing pixels and the frame bufferto output the image data to the frame buffer; a second read line coupledbetween the self-powered pixels and the frame buffer to output thephotocurrent to the frame buffer; and an energy accumulator configuredto store electrical energy of the photocurrent via a charge path betweenthe self-powered pixels and the energy accumulator.
 2. The sensor deviceas claimed in claim 1, further comprising a multiplexer configured tocouple the frame buffer to the first read line or the second read line.3. The sensor device as claimed in claim 1, wherein the self-poweredpixels are arranged at a part of pixel rows or pixel columns of theimage sensing array, and the part of pixel rows or pixel columns of theself-powered pixels are not adjacent to each other.
 4. The sensor deviceas claimed in claim 1, wherein the sensing pixels and the self-poweredpixels are arranged as a checkerboard pattern.
 5. The sensor device asclaimed in claim 1, wherein the sensing pixels are configured to outputthe image data in a displacement detecting mode but not to output theimage data in a steady state mode.
 6. The sensor device as claimed inclaim 1, wherein the self-powered pixels are configured to output thephotocurrent in both a displacement detecting mode and a steady statemode.
 7. The sensor device as claimed in claim 1, wherein the energyaccumulator is configured to provide the stored electrical energy to alight source.
 8. The sensor device as claimed in claim 1, wherein theframe buffer is configured to store the image data in a displacementdetecting mode, and in a steady state mode, the frame buffer is coupledto the self-powered pixels but not coupled to the sensing pixels; andconfigured to store intensity data corresponding to the photocurrent. 9.The sensor device as claimed in claim 8, wherein the steady state modeis left according to a value variation of the intensity data in theframe buffer.
 10. The sensor device as claimed in claim 8, wherein inthe displacement detecting mode, the self-powered pixels are not coupledto the frame buffer.
 11. A sensor device configured to be operated on aworking surface, the sensor device comprising: a frame buffer; an energyaccumulator; and an image sensing array configured to sense reflectedlight from the working surface, the image sensing array comprising: aplurality of sensing pixels configured to respectively output image dataaccording to the sensed reflected light, each of the sensing pixelscomprising a read switch configured to control the outputting of theimage data to the frame buffer; and a plurality of self-powered pixelsconfigured to respectively output photocurrent according to the sensedreflected light, each of the self-powered pixels comprising an energystorage switch configured to control the outputting of the photocurrentto the energy accumulator to cause the energy accumulator to storeelectrical energy of the photocurrent.
 12. The sensor device as claimedin claim 11, wherein each of the self-powered pixels further comprisesanother read switch configured to control the outputting of thephotocurrent to the frame buffer.
 13. The sensor device as claimed inclaim 12, further comprising a multiplexer configured to couple theframe buffer to the self-powered pixels or the sensing pixels.
 14. Thesensor device as claimed in claim 12, wherein the read switch and theanother read switch are triggered by a row selection signal provided bya timing controller.
 15. The sensor device as claimed in claim 11,wherein the energy storage switch is triggered by an energy storagesignal provided by a timing controller.
 16. The sensor device as claimedin claim 11, wherein the self-powered pixels are arranged at a part ofpixel rows or pixel columns of the image sensing array, and the part ofpixel rows or pixel columns of the self-powered pixels are not adjacentto each other.
 17. The sensor device as claimed in claim 11, wherein thesensing pixels and the self-powered pixels are arranged as acheckerboard pattern.
 18. The sensor device as claimed in claim 11,wherein the sensing pixels are configured to output the image data in adisplacement detecting mode but not to output the image data in a steadystate mode.
 19. The sensor device as claimed in claim 18, wherein in thedisplacement detecting mode, the self-powered pixels are not coupled tothe frame buffer.
 20. The sensor device as claimed in claim 11, whereinthe energy accumulator is configured to provide the stored electricalenergy to a light source.